A case report of a paranasal sinus mucocele ABSTRACT OBJECTIVE: We present here a case of an extensive frontoethmoidal sinus mucocele complicated by a right eye proptosis, and given its clinical manifestation, we present our approach of this case as well as analyze its aspects. Also, we discuss the diagnostic imaging techniques used, the treatments applied, other therapeutic alternatives, and postoperative results. CASE REPORT: A 47-year-old man had right eye proptosis, visual turvation, tearing, nasal congestion, and hyposmia. A computed tomography showed a well-defined mass in the frontal and ethmoid sinuses with right intraorbital extension. A nasal endoscopic surgical excision was performed, after which a great improvement in the presenting symptoms occurred immediately after surgery. CONCLUSION: Frontoethmoidal mucoceles are benign and curable with the use of nasal endoscopic techniques. However, early diagnosis and treatment are of paramount importance, as these mucoceles are capable of causing not only simple local complications, but also more serious ones at the orbital and intracranial levels.